POS0041 UPREGULATION OF SSP1 (OSTEOPONTIN) BY ADIPOSE TISSUE-DERIVED MESENCHYMAL STEM CELLS OCCURS WITH THE CONTINUOUS MECHANICAL LOAD BUT IS STRONGLY RESTRICTED IN INF-G/TNF-A/IL-22 MICROENVIRONMENT
Authors: A. Shouval, M. Brant-Roznavi, T. Tamari, H. Hazan-Molina, D. Aizenbud, S. Keret, L. Saiegh, G. Slobodin
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> The interplay between the inflammatory part of the disease and osteogenesis in axial spondyloarthritis (AxSpA) is incompletely understood. It is believed that inflammation triggers the process of new bone formation on the one hand, but the regulation of these phenomena is distinct on the other. An assumption that disease-related osteoproliferation in AxSpA is governed by the complex interplay of inflammation, hormonal or growth factors, and mechanical load has been made. A recent study demonstrated that a pro-inflammatory environment, consisting of interferon-γ (INF-γ) and tumor necrosis factor-α (TNF-α), allowed IL-22-induced proliferation and migration of mesenchymal stem cells (MSc) [1]. <h3>Objectives</h3> To examine the influence of continuous mechanical load (CML) on the osteogenic behavior of MSc with or without INF-γ/TNF-α/IL-22 or testosterone exposure. <h3>Methods</h3> Adipose tissue-derived MCs, characterized by CD90<sup>+</sup>, CD73<sup>+</sup>, CD13<sup>+</sup>, CD45<sup>-</sup>, CD31<sup>-</sup>, isolated from the adipose tissue of a healthy donor and kindly donated by Bonus BioGroup, Haifa, Israel, were cultured for two weeks without or under CML of 2 gr/cm<sup>2</sup>, applied by transparent glass cubes placed on the plates covering the well, in the following conditions: a. osteogenic differentiation medium (ODM) with no additions of cytokines or testosterone; b. ODM with the addition of testosterone, 0.01 µM; c. ODM with the addition of INF-γ (2.5ng/ml), TNF-α (1ng/ml), and IL-22 (0.5ng/ml); d.ODM with the addition of both three cytokines above and testosterone. Real-time PCR for <i>ALPL, RUNX2, SPP1, BMP2,</i> and <i>Col1A1</i> was performed and analyzed by the ThermoFisher cloud data analysis program (https://thermofisher.com/il/en/home/digital-science/thermo-fisher-connect/all-analysis-modules.html). ΔΔCt and RQ (2<sup>-ΔΔCT</sup>) were calculated, with the results presented in a histogram graph as fold-change (Figure 1). <h3>Results</h3> CML induced significant upregulation of <i>SSP1</i>, or osteopontin (OPN), by MSc. However, this effect was almost completely abolished in the presence of INF-γ/TNF-α/IL-22. <h3>Conclusion</h3> Increased OPN production by MSc can link mechanical load and new bone formation after the resolution of the inflammatory phase in AxSpA. <h3>Reference</h3> [1]El-Zayadi AA, Jones EA, Churchman SM, et al. Interleukin-22 drives the proliferation, migration and osteogenic differentiation of mesenchymal stem cells: a novel cytokine that could contribute to new bone formation in spondyloarthropathies. Rheumatology (Oxford). 2017;56:488-493. <h3>Acknowledgements</h3> Genomics Center of Technion, Haifa, Israel, for performing real-time PCR tests for the study. <h3>Disclosure of Interests</h3> Aniela Shouval: None declared, Marina Brant-Roznavi: None declared, Tal Tamari: None declared, Hagai Hazan-Molina: None declared, Dror Aizenbud: None declared, Shiri Keret: None declared, Leonard Saiegh: None declared, Gleb Slobodin Speakers bureau: Novartis, Abbvie, Pfizer, Eli Lilly, Sanofi, Grant/research support from: Novartis.